storage of food and initial digestion of proteins + fats; production of the hormone gastrin (response to protein) that stimulates stomach's gastric glands to release gastric juice (including pepsin and HCl)

small intestine

continued digestion of carbohydrates, proteins, lipids; most absorption of nutrients; production of the hormone secretin (response to HCl) that stimulates pancrease to release bicarbonate; production of the hormone CCK (response to fat) that stimulates gall bladder to release bile

pancreas

production of digestive enzymes that act in small intestine; production of the hormones insulin and glucagon which regulate blood sugar; production of bicarbonate that neutralizes stomach acid in small intestine

large intestine

absorption of water; production of some vitamins; storage of undigested food